The present invention relates generally to devices for detecting flash events and, more particularly, to a method and apparatus for detecting lightning and rapid pulse light flashes.
The detection of lightning and rapid pulse light flashes have numerous applications ranging from photography, lightning protection devices, the detection of muzzle flashes and the like.
Prior art devices have provided the ability to detect lightning flashes, however they have lacked the ability to perform this function with sensitivity and selectivity necessary to be functional. Furthermore, they have lacked the ability to detect flashes as well during the day or at night.
For the purpose of this invention, an apparatus for the detection of lightning and rapid pulse light flashes have very similar design characteristics and wherein such an apparatus can perform the detection of rapid pulse light flashes and various forms of lightning through the use of properly selected filtering techniques. Furthermore, such a device can be provided wherein detection sensitivity is constant throughout the daytime and at night.
Lightning photography is a popular form of artistic expression commonly found in pictorial books and magazines. Such dramatic photographs of bolts of lightning have great visual impact.
Scientific uses of lightning photography are also well known to those skilled in the art. Lightning photography with conventional cameras is restricted to the well-known practice of using long exposure times, usually at night or in low ambient light levels. The lightning event is captured on film during the time period when the camera shutter is held open, which is typically five to ten minutes, requiring the use of a camera tripod.
However, the methods of the prior art are tedious and time consuming and do not provide for lightning photography during normal daylight hours. Further, the photographer must remain out of doors with the camera equipment and be exposed to the hazards of lightning.
Thus, the present invention has been developed to provide a lightning trigger device capable of interfacing with many commercially available cameras having sufficiently fast shutter lag times during both daylight and nighttime conditions.
In addition, the present camera triggering method can be practiced by utilizing the camera""s remote shutter release, thereby photographing lightning events from a safe distance. Further, the cost of the present lightning trigger device is substantially lower in comparison to other automated methods of photographing lightning.
The present invention may also be utilized to detect the initiation of the stepped leader phase of the lightning event for preemptively disconnecting susceptible electronic and electrical devices via fast acting relays before the incipient and destructive return stroke occurs. Devices that may benefit by preemptive protection from the damaging effects of the return stroke and subsequent electromagnetic pulses (EMP) include electronic and electrical devices such as computers, telephones, household and industrial appliances, and the like. Back up power supplies may be incorporated with the lightning trigger detection device to ensure continuous operation and protect against a loss of service, data or critical operation.
The present invention may also be utilized to detect rapid pulse light flashes produced by sources such as a muzzle flash form a gun wherein an indication device or associated equipment may be activated in response thereto.
U.S. Pat. No. 5,184,215 to Barker discloses an automated system for detecting and recording lightning strikes in the vicinity of power lines. In one embodiment of the invention, the automated system includes a toroid surge sensor; a phototransistor optical sensor located within a pole mounted housing; a magnetic loop sensor; a control circuit for one or more cameras and/or video camcorders; and a power supply all contained within a weather-tight housing. Such a system clearly lacks portability and is designed specifically for the monitoring of electrical power transmission utilities.
U.S. Pat. No. 5,448,161 to Byerley et al. discloses an optical radiation detector for lightning or other light signals such as pulses, bursts, flashes, and steady fluctuations. A silicon photodiode or other light-sensitive silicon device is arranged to receive light signals in the infrared, visible, ultraviolet, and wide-band ranges, etc.
U.S. Pat. No. 3,759,152 to Fletcher discloses a system for monitoring and recording lightning strikes within a predetermined area with a camera having an electrically operated shutter and means for advancing the film in the camera after activating the shutter. The system includes an antenna for sensing electrical field changes which generate a signal that is fed to an electronic circuit for operating the shutter of the camera.
U.S. Pat. No. 3,712,195 to Harvey discloses an apparatus for photographing meteors in a selected area of the sky only at times meteors are likely to be passing through the area. A photo multiplier is pointed in the direction of the designated area. When a meteor passes through the area, the signal output of the photo multiplier increases, activating a camera.
U.S. Pat. No. 3,700,336 to Clegg discloses a method for optically detecting lightning radiation in both daylight and nighttime conditions. A silicon solar cell receives light radiation, converting them to electrical signals which are amplified and electronically processed for recording purposes. However, this apparatus is not used in conjunction with photographic equipment.
U.S. Pat. No. 3,934,259 to Krider discloses an all-sky camera apparatus for time-resolved lightning photography. This invention utilizes a pair of all-sky cameras which are disposed with their respective lenses pointing vertically. One of the cameras is rotated about an axis passing through the zenith while the other is maintained in a stationary disposition to determine the time development of lightning discharge.
U.S. Pat. No. 5,255,038 to Suzuka discloses a remote control apparatus of a camera having a camera body with a finder eyepiece window including an infrared receiver which is associated with the shutter of a camera body. A remote release signal emitted from an infrared transmitter is received by the infrared receiver to release the shutter of the camera body.
U.S. Pat. No. 4,707,127 to Goedken discloses an auto-wireless shutter release control that will allow the user to take a photograph by remote control.
U.S. Pat. No. 4,051,496 to Iida et al. discloses a remote control camera having a fitting member for mounting thereon a signal receiving device to receive a remote control signal, the body of the signal receiver, when fitted on the camera body, serving to cover the entire eye-piece on the camera body to intercept light entering into the camera body through the eye-piece.
U.S. Pat. No. 4,926,284 to Eugenio discloses a lightning protection device for directly sensing a predetermined critical electrostatic field intensity of the stepped leader to prevent the formation of the return stroke. The device uses a charge storing sphere and a varistor grounding device to dissipate the charge of the otherwise incipient return strokes.
U.S. Pat. Nos. 5,521,603 and 5,297,208 to Young disclose are electric field sensing devices for lightning detection and method for deactivating electrical equipment.
U.S. Pat. No. 4,276,576 to Uman discloses a lightning protection device utilizing electric or magnetic field responsive detectors and means for isolating or grounding electrical equipment.
U.S. Pat. No. 5,057,820 to Markson et al. discloses an optical warning system for distinguishing between strobe light flashes and lightning flashes and providing audio and visual indication of detection to an operator.
After much study of the above described problems, the present invention has been developed to provide a lightning trigger and flash detection device. In photographic applications, the invention will provide the artistic and/or recreational photographer with a compact, lightweight device which allows the user to safely obtain lightning photographs using a handheld camera while inside a car, house, or other protected structure.
The user may also use the lightning trigger and flash detection device attached to such a handheld camera mounted on a camera tripod when photographing lightning events from a safe distance utilizing the camera""s remote electronic or infrared shutter release.
The lightning trigger and flash detection device can also be used as a sensor for utilizing the initiation of the stepped leader for preemptive protection of electrical and electronic devices before the damaging return strokes can occur.
More particularly, the photographic lightning trigger and detection device functions to detect an unregulated, omni-directional flash of light by the use of a photodiode sensor and a trans-impedance amplifier with an automatic variable gain control which causes the camera shutter to be released in response to the lightning flash. The device further incorporates a timing function for preventing undesirable repetitive film exposures when through-the-lens method of sensing of the lightning flash is utilized.
Furthermore, in photographic applications, the automatic camera metering circuits may be preactivated for minimizing the camera shutter lag time while at the same time isolating the camera and lightning trigger voltage supplies.
Detection may be accomplished in several manners utilizing distinctive characteristics of the lightning flash. Whereas, prior art detection methods rely upon sensing the wide-band event of the lightning flash or the presence of unusually high electromagnetic field intensities for predicting lightning activity, the present invention employs the additional preemptive benefit of detecting the stepped leader. Two significant characteristics suitable for detection are utilized; the pulsing propagating components of the stepped leader, and the relatively long duration between the initiation and completion of the stepped leader.
The lightning trigger and flash detection device can also be used to detect light flashes from unregulated or regulated, non-natural point sources such as flash strobes and muzzle flashes. In flash detection applications, such as those caused by muzzle flashes a threat indicating system can be employed to alert and/or activate associated equipment.
Furthermore, through the selection of the appropriate filtering/coupling circuit, motion detection can be accomplished by the sensing change of reflected light off moving objects and thence incident upon the flash detection sensors.
Accordingly, the invention may be employed to benefit several forms of existing technologies and practices, lightning photography and detection, motion detection and flash event detection being advantageous applications.
In view of the above, it is an object of the present invention to provide a photographic lightning trigger device which is practical for use by the artistic and/or recreational photographer using a handheld camera.
Another object of the invention to provide a sensing system for detecting the initiation of the stepped leader phase of a lightning stroke for the protection of auxiliary electrical loads.
Another object of the present invention is to provide a photographic lightning trigger device which functions to respond to an unregulated, omni-directional light event and to instantaneously cause the camera shutter to be released.
Another object of the present invention is to provide a sensing device for the detection of rapid pulse light flashes and the controlling of associated equipment.
Another object of the present invention is to provide a method for optically detecting events utilizing a photodiode and trans-impedance amplifier with an automatic variable gain control for use in conjunction with a handheld camera or other auxiliary devices.
Another object of the present invention is to provide a method for enhanced flash impulse detection while maintaining constant sensitivity to varying ambient conditions by utilizing non-linear amplification and variable threshold comparator means.
Another object of the present invention is to provide a device that allows the user to safely obtain lightning photographs using a handheld camera while inside a car, house, or other protective structure.
Another object of the present invention is to provide a photographic lightning trigger device which enables lightning photography to be performed during both daylight and nighttime conditions.
Another object of the present invention is to provide a photographic lightning trigger device of a lightweight and compact size which may be integrated into the camera housing, mounted directly onto the camera shoe fitting, or incorporated into a small pocket-sized enclosure.
Another object of the present invention is to use fiber optics for focusing a lightning flash sensor to the field of view of the camera lens.
Another object of the present invention is to provide a preemptive lightning sensor for protecting electrical devices from lightning related electrical damage.
Another object of the present invention is to provide a means for minimizing the shutter lag time prior to recording a lightning flash.
Another object of the present invention is to provide a means for motion detection and controlling an auxiliary device.
Another object of the present invention is to provide for a method of sensing the initiation of the stepped leader and controlling an auxiliary device prior to the occurrence of the return stroke.
Another object of the present invention is to provide a selectable mode for detecting cloud to ground and multiple impulse flashes and to reduce film consumption.
Another object of the present invention is to provide for a method of protecting electronic and electrical devices through the use of lightning trigger-detection device by preemptively disconnecting and protecting electronic devices from damaging electrical surges before the subsequent return strokes occur.
Another object of the present invention is to provide a means of flash detection wherein the sensitivity to flash or impulse events is constant throughout varying ambient levels.
Another object of the present invention is to provide a means of RF impulse detection wherein the sensitivity to flash or impulse events is constant throughout varying background noise levels.
Another object of the present invention is to provide for a method of multi-mode rapid pulse flash, motion detection and ground flash detection device for controlling associated equipment.